German utility model publication DE 201 02 619 U1 discloses a display for a solar power system. In the display, a day target curve of the power produced by the solar power system is calculated. This day target curve is then continuously fitted to the actually possible power of the particular solar power system by learning under error-free conditions. A precondition for this procedure is an additional measurement of the solarization intensity actually present. The first day target curve is calculated depending on the location of the solar power system (latitude and longitude) and the seasonal position of the sun which is adjusted daily or monthly. In this way, environmental limitations to the optimum orientation of the photovoltaic modules of the solar power system have an impact on the first daily curve. If, after the learning phase, the actual value of the power produced by the solar power system differs from the learned target curve by more than an adjustable degree, this is pointed out to the user. In the known display, repeated shadowing events affecting the photovoltaic modules of the solar power system have an influence on the learned target curve. However they are neither recognized as such nor assessed with regard to their importance.
A method of controlling a solar power system comprising several photovoltaic modules is known from DE 10 2006 008 178 A1. Here, comparative measurements between the individual photovoltaic modules are performed for a permanent power control. If deviations between the measurement values occur, these are interpreted as an indication that the photovoltaic system needs a revision. With regard to the deviations occurring, it shall be differentiated between whether it is an environmental disturbance like shadowing by clouds, trees or immovables, or an irreversible mechanical or electrical damage. Details enabling this differentiation, however, are not found in DE 10 2006 008 178 A1.
There still is a need for a method which enables recognizing shadowing of a photovoltaic module with high reliability and which thus provides a basis for suitably assessing the consequences of the respective shadowing.